Compressive crushing of granite with wear-resistant materials

Uniaxial crusher is a non-standard wear testing device designed and used at the Tampere Wear Center for evaluating the wear resistance of materials in compressive crushing. In this study, various wear resistant materials were tested and their wear surfaces characterized with scanning electron microscopy. In addition, the general suitability of the device for wear testing was evaluated. Abrasive wear was the most common wear mechanism observed on the studied surfaces. Moreover, marks of surface fatigue were also seen. The material loss was mostly due to plastic deformation. Higher hardness was found to correlate with improved wear resistance, especially in cases where wear was purely abrasive

Effect of abrasive properties on the high-stress three-body abrasion of steels and hard metals

Especially in tunneling, the abrasiveness of rock is an important property, which can easily be determined by several methods developed for the purpose. With this in mind, it is rather surprising that the effects of different rock types on the wear mechanisms of engineering materials have not been too widely studied. In this paper, high stress three-body abrasive tests were conducted with four different abrasives with a relatively large (2-10 mm) particle size. As test materials, three different steels and three hard metals were used. The tests clearly showed that material type has an influence on how different abrasive and material properties affect the abrasive wear mechanisms and severity. For example with hard metals, the most important property of the abrasives is their crushability, as only small abrasive particles are able to properly attack the binder phase and cause high wear rates. On the other hand, it seems that the abrasiveness of rock is not the dominating property determining the severity of wear in the current test conditions for any of the tested materials. In fact, with steels no single abrasive property could be shown to clearly govern the abrasive wear processes. In any case, when using the determined abrasiveness values in wear estimations, the contact conditions in the method used for determining the abrasiveness values should be as similar as possible with the end application

Ooppera Viimeiset kiusaukset Joonas Kokkosen säveltäjäkuvan heijastumana

The purpose of this study is to map out Joonas Kokkonen's entire output up to the present time (1948-87) and to examine in particular the opera Last Temptations (1975) in the light of the composer's earlier production but also to trace its relationship to works composed subsequently. The problem is twofold. First, what exactly is the internal, and the surface structure of Last Temptations; and second, what theme materia!, and what features of the structure, are derived from the composer's earlier work? The hypothesis put forward about the internal structure is that Kokkonen' s works consist of five phases: a theme-statement, its reiteration, a further development of the theme, and a resolution of this into, finnally, a return to the beginning. (Exposition, re-iteration, development, metamorphosis, and return). Further, the opera's symbolism forms part of (is an integral part of) its internal structure. The surface structure is examined from three angles: the golden section; the dialogue between the dramatic and lyrical contents, and the musical density. The form of Last Temptations is approached mainly from the point of view of its developmental processes. The study is based on Ilkka Niiniluoto's theory of varieties of meaning (of signification) and Göran Hermeren's five variables for interpretation, together with some other theoretical models. Thus the approach of this study is basically multilateral. The study has shown that Last Temptations owes a great deal of its melodic and structural content to the composer's earlier work; and that the same motifs run through Kokkonen's music from one work to the next. The chromatic starting-point, the symphonic theme, the way in which the work develops (the pattern of development), the golden section, the horror-of-vacuum principle, the density of the music and the melodic field make up the greater part of our picture of Joonas Kokkonen the composer

The effect of test parameters on large particle slurryerosion testing

Understanding the effect of testing parameters is important for getting the test environment as close as possible to real applications and for understanding the processes that are involved in the testing itself. A pin mill type slurry-pot wear tester was developed for heavy-duty testing with high speed and large abrasive size [1]. This study focuses on the effect of different testing parameters on large particle slurry testing. Parameters such as rotation speed of the samples, particle size and slurry concentration were varied. Round steel samples and slurry with water and granite gravel were used for testing. The test parameter variations were 4 to 10 mm for granite particle size, up to 23 wt% for slurry concentration and up to 20 m/s for sample tip speed. The relationship between the particle size, slurry concentration, and the amount of particles are discussed. Also the role of the kinetic energy of the abrasive particles is considered for large particle sizes.acceptedVersionPeer reviewe

Specific wear energy in high-stress abrasion of metals

A certain amount of mechanical work is always needed for wear to occur in an operational system. The estimation of this work based on the measured electrical energy input is, however, usually quite difficult. The dual pivoted jaw crusher was designed to allow accurate wear and work measurements during the tests, enabling the division of consumed energy to specific wear and crushing energy portions. The major contributors to the specific wear energy are the frictional contacts during the sliding movement. In this work, high stress abrasion wear tests were conducted with several metals ranging from pure aluminum and copper to carbide-reinforced steels, and the specific wear energy was correlated to several material properties. The results show a linear correlation between some of the material properties and the specific wear energy, whereas a similar comparison of the material properties with the amount of wear or work done during the tests yields a non-linear correlation

Correlation of wear and work in dual pivoted jaw crusher tests

A laboratory sized jaw crusher with uniform movement of the jaws, the Dual Pivoted Jaw Crusher (DPJC), was used to determine the relationship between wear and work. Wear was concentrated on the jaw plates opposing each other and was measured as mass loss of the specimens. Work was measured directly from the force and the displacement of the instrumented jaw, which allowed work to accumulate only from the actual crushing events. The tests were conducted with several jaw geometries and with two motional settings, where the relation of compressive and sliding motion between the jaws was varied. The comminution of rock is presumed to be irreversible, meaning that the energy used for crack formation in the rock particles eventually results in the fracture of the particles. Therefore, the amount of energy needed to comminute rock particles should be roughly constant and not dependent on the loading conditions, if the speed of the loading contact is not changed. The DPJC test method allows the separation of work components into comminution specific work and sliding specific work. The results can be used to compare the crushability of minerals without the influence of the used test geometry or the selected jaw plate materials. The sliding work can be used for the comparison of the wear of the jaw plate materialspublishedVersio